Declining sperm counts could lead to human extinction

The human race could struggle to pro-create future generations according to a researcher who has revealed dwindling sperm counts in men across the globe.

"Eventually we may have a problem, and with reproduction in general, and it may be the extinction of the human species," Dr Hagai Levine from the Hebrew University of Jerusalem, told the BBC after publishing his grim findings.

His assessment - Human Reproduction Update findings – is one of the largest ever undertaken and combines extensive results from 185 studies dating back to 1973.

The study revealed sperm counts in men from North America, Europe, Australia, and New Zealand had halved in less than 40 years.

However, the same decline had not been identified in men from South America, Asia and Africa.

The cause of the decline has been linked to a plethora of factors, including exposure to chemicals, obesity, smoking, diet, stress and watching too much television.

Dr Levine's findings are not without its detractors with critics pointing out potential flaws in the study.

One argument is that the men being screened are usually frequent visitors to fertility clinics and have naturally lower sperm counts as a result.

Another is that early sperm count tests were fallible because they often overestimated the final results.

Professor Allan Pacey from Sheffield University told the BBC that while there was merit to Dr Levine's study it was irresponsible to not question the findings.

"The debate has not yet been resolved and there is clearly much work still to be done. However, the paper does represent a step forward in the clarity of the data which might ultimately allow us to define better studies to examine this issue," he said.